[BC] The XLR pinout debate

[Mark Humphrey]

On 8/13/06, Stevan A. White <w5saw at pathwayz.com> wrote:

> I have an old Symmetra-Peak I found several years ago and will never let it
> go.  It proudly lives in my ham station audio chain along with a mic
> processor and a couple other items.  It is the "secret" to my nice, smooth,
> clean and almost too loud FM and SSB audio.  I believe what it is is an
> all-pass filter does that minimizes phase distortion and asymmetry.  Is that
> right, Leonard?

I'm not sure if Leonard frequents this reflector, so I'll mention that
most of the design details are in his patent for the Symmetra-Peak,
which you can find by searching the uspto.gov website.  It's patent
no. 3,060,389 from October 23, 1962.

Gary, W3AM, also has a nice description on his website:

http://www.w3am.com/8poleapf.html

Take a look at a square wave after it passes through the box and
you'll see that the circuit actually introduces phase distortion --
lots of it -- but that's what reduces the vocal asymmetry.  I first
learned about the Symmetra-Peak (back when I was in high school) from
Vince Mangiameli, former CE of WOLF in Syracuse, in a quest to find
out why his little 1 kW transmitter on 1490 sounded so much better
than the 5 kW AMs in town.

I have one in my ham station, too -- along with a Kahn "Good-n-Loud"
(aka the Non-Symmetra-Mod), which makes a waveform asymmetrical again
(on a controlled basis) by amplifying the positive half with a higher
gain than the negative half.

Mark
K3XY